More Opteron musings - Jay Maynard

> Recent entries
> Calendar view
> Friends page
> User info
> Jay's web page

Thursday, 30 June 2005


Previous Entry Share Next Entry
0931 - More Opteron musings

With some help from youngvanwinkle's guide to AMD 64-bit CPUs, I've gone looking for parts for a nice Hercules engine. This system will be a compute engine only, and not on my desktop at all (it'll live in the machine room behind a PS/2 KVM switch, so I need PS/2 keyboard and mouse). I don't care about blazing graphics performance. I'll install Gentoo on it, building from stage 1.

Here's what I've come up with:
Two Opteron 244s: $406
MSI K8T Master 2-FAR dual socket 940 motherboard: $248
2 1GB ECC/registered DDR400: $240
250 GB Serial ATA hard disk: $105
DVD-ROM: $30 or so
Case, floppy, power supply (550W, I assume, will be needed), and so on: $100
Total: $1129

If I substitute an Asus K8N-DL motherboard, the price goes up $26, to $1155. That's an approximation, and doesn't include little details like shipping, but it's a ballpark number. The Opteron 244, 1 GB DIMM, and 250 GB drive all represent the knee of the price/capability curve.

The difference in price between the Opteron and the consumer-grade Athlon 64 is not big at all when you back off from the absolute top of the line. Two CPUs are better than one faster one for this job because Hercules is heavily multithreaded, and quite good at keeping multiple CPUs busy. Two separate CPUs beat one dual-core CPU for bang for the buck right now; if I get hungry for more performance, I'll replace the processors later.

I dunno if I'll buy it right away, but at least a good fast box isn't out of reach.

current mood: [mood icon] contemplative
current music: Peter Gabriel - In Your Eyes

(12 comments | Leave a comment)

Comments:


[User Picture]
From:shelbystripes
Date: - 0000
(Link)
There are two real reasons you want the Asus K8N-DL board. One is that it comes with the newest nForce4 Pro chipset and all the features that come with it, an important one being the onboard PCI Express slots. AGP is a rapidly dying tech, and PCI-E is very much gonna be the way to go. I know that won't matter much for a server, but who knows what you'll be doing with this thing in the future, and besides, there will soon be a variety of Gigabit Ethernet, RAID, and other cards that could populate those PCI-E slots. The newer board/chipset also means it ships out of the box with dual-core Opteron support; if Hercules is so heavily multithreaded, then you'll very much want to keep the option to upgrade to dual-cores when prices drop on them.

The second and more important reason is the number of DIMM slots. That MSI board only has four DIMM slots, all of which are tied to the same Opteron CPU. Like I mentioned in the "review", the K8 core has an integrated memory controller; if you have two physical CPUs, then you end up with two memory controllers, each of which can support up to four DIMMs. This means a dual-Opteron board can support up to eight DIMMs, and while that's impractical on even an E-ATX board, Asus managed to cram 6 DIMM slots on that K8N-DL board, four tied to one CPU and two to the other.

And even more important than that, if you use both memory controllers, you get double the total memory bandwidth. If the memory bus is, say, 8GB/s (this is an example), and you have memory attached to both CPUs, each CPU can have their own 8GB/s transactions going on at the same time, so you have a total of 16GB/s of bandwidth available.

You don't have to have memory hooked up to each CPU to start. You can just plug two DIMMS into one bank connected to one CPU, and the second CPU will access that RAM through the first. But when you upgrade to more RAM later, you'll want to put it on the CPU that's not got any RAM on it yet. That gives you a bandwidth upgrade.

Also, just so you know... $100 is unrealistic for an Extended ATX form factor case and power supply, especially since a good power supply is key to a stable system. Highly recommended for this project is the Antec TruePower 550W EPS12V power supply. You can't just use any 550W PSU, you need one that's EPS12V compliant with both a 24-pin motherboard connector and additional 8-pin 12V connector for those boards. There's a new revision of the PSU, too, the TruePower 2.0; the newer one will be more expensive, but that means it's also driving the price of the older model down if you can still find it.

Such a power supply is mandatory; all workstation-class motherboards will call for EPS12V spec power, and no consumer-level PSUs provide both the 24-pin primary and 8-pin auxiliary 12V rail that such a spec requires.

Expect to pay around $100 for a good power supply, Antec or not. But that's $100 plus a case to go with it, and it'll cost another chunk to get a case big enough to hold an Extended ATX board, which all these dual-proc boards are.

Actually, looking it up, Antec actually makes an Extended ATX spec case that comes with that power supply (the 2.0 version) that's specifically marketed for dual-Opteron motherboards. Given its sheer size it's aptly named the "Titan"; it retails for $220 on NewEgg though you might find it cheaper if you shop around.

Since any case you buy would come with a crap PSU you'll have to chuck out, you may as well buy a case that comes with the PSU you'll actually want.

So, budget $220 for case and PSU. As a final suggestion, since that's a black case, get a black-faceplate DVD-ROM and floppy drive. Such things don't really command a price premium anymore; you just have to look a little to find them.
[User Picture]
From:jmaynard
Date: - 0000
(Link)
EATX cases seem to run over $100, so that Antec case/PS seems like a good deal. Okkay, it's in.

I know Asus builds good stuff, so the extra $25 for that one seems like a no-brainer. I do have to wonder how much of a penalty one CPU incurs for accessing memory through the other CPU's memory controller, but I'm sure AMD has thought about that one a long time ago.

Can I stuff a plain old PCI graphics controller in a PCI-X slot, or will I have to shell out for a PCI-X graphics controller? I'm not particularly interested in spending a couple hundred bucks on a graphic controller that won't do me any good now and will likely be thoroughly outdated should I ever decide to run the box as a desktop.

Hercules is quite good at keeping all the CPUs you can throw at it busy. When I was at Compaq, I tried it on an 8-way Proliant 8500, and it handled a truly remarkable load under emulation. While the CPU emulation can only use one CPU at a time per emulated processor (although it can emulate up to 16 IBM CPUs), there are other threads running all the time, as well as a pool of threads to handle emulated I/O requests. The latter, especially, will overlap nicely with CPU emulation, in just the same way that an IBM mainframe will overlap I/O and CPU, and IBM OSes are designed to take maximum advantage of the concurrency.
[User Picture]
From:sideband
Date: - 0000
(Link)
You guys need to stop.. No really.. I'm sitting here in the truckstop drooling, and getting funny looks..

::wipes mouth::
[User Picture]
From:shelbystripes
Date: - 0000
(Link)
Asus = good.

There is a minor performance penalty for one CPU accessing RAM from the other, but it's really not a big deal, since even those kind of accesses tend to be faster than the traditional Intel go-to-northbridge-for-memory-access method. And, of course, the fact that all Opteron CPUs come with 1MB cache each helps with that considerably, also.

You can put in a plain PCI graphics card, sure. There are no "PCI-X" slots on that Asus motherboard; PCI-X is an extension of the old PCI bus to 64-bit and up to 133MHz operation, but it's a longer slot and you can shove old PCI cards in it and they'll operate, albeit at the old 32-bit rate. PCI Express ("PCI-E") is totally different; it's software-compatible with PCI, but the connector's different, and you can't plug old PCI cards into it. However, that Asus board does have two plain old PCI non-X non-E cards that you can shove a video card in and it'll work fine. If you have an old PCI card laying around, an ATI Rage XL or something, you should just be able to stick it in one of the board's regular old PCI slots.
From:timp87
Date: - 0000
(Link)
Where are those prices from? $105 for a 250GB SATA drive seems too good to be true.
[User Picture]
From:jmaynard
Date: - 0000
(Link)
Pricewatch lists lots of computer parts, by advertised price. It's where I usually go to find parts.
[User Picture]
From:shelbystripes
Date: - 0000
(Link)
One more recommendation for you: Buy everything from NewEgg. Their prices are typically very competitive, not the cheapest but definitely close to it, and where they make up for it is in the customer service. I bought a hard drive from them that was just dead, kept locking up in the same spot every time I'd try to format it. Did an online RMA request, got an RMA number, shipped it back, had a new hard drive a couple days later, everything was solid.

That kind of thing can happen with any online vendor. NewEgg has a good reputation for being easy to do returns with, which given that most of the time they have the lowest price, makes them worth sticking with even when it occasionally costs a buck or two more there than elsewhere.
[User Picture]
From:jmaynard
Date: - 0000
(Link)
I've created a NeEgg wish list for this configuration...it comes in at $1420. I went with the retail version of the Opteron, with heatsink and fan; an NEC DVD burner, because it was $13 more than a DVD-ROM; and a WD Caviar RE drive because it's rated for 7x24 service, something important in this application. Everything but the motherboard is in stock.
[User Picture]
From:jmaynard
Date: - 0000
(Link)
Oh...forgot the NewEgg link: The Hercules engine.
[User Picture]
From:shelbystripes
Date: - 0000
(Link)
There you go. You have a name for this yet-unbuilt beast? "mephit" is still available, I'm sure... *hides*
[User Picture]
From:jmaynard
Date: - 0000
(Link)
It'll get an Animaniacs character name. I haven't picked one yet.
[User Picture]
From:foolscap001
Date: - 0000
(Link)
What Mephit said... but if you do consider it wise to buy elsewhere, hit http://www.resellerratings.com/ first, and see what people have to say about the place you're thinking of buying from.

> go to top
LiveJournal.com